Safety helmets are indispensable items of safety equipment for a wide variety of purposes such as riding a bicycle or motorcycle, functioning in hazardous work environments, and also for a variety of recreational sports. Generally, a helmet is structured to provide shock-absorption properties so as to protect a wearer from potentially deadly injury resulting from a direct blow to the wearer's head. Existing helmet designs typically include a substantially rigid outer shell, with the inside of this rigid outer shell being typically lined with a combination of foam and rubber-like padding which tightly surrounds a wearer's head on an underside of the helmet surface. The materials utilized in forming such helmets usually include a deformable synthetic foam material. In the event of a direct blow to the hard outer shell of the helmet, the force of the blow is transferred to the foam and rubber-like padding surrounding the helmet assembly. Upon an impact to the helmet surface, the foam and rubber-like padding deform in a gradual manner so as to absorb a portion of the impact energy and reduce the effects of the impact upon the wearer.
Bicycling is an international recreational activity and means of transport that maintains a serious risk of head injury. In addition to bicycling other recreational activities including rollerblading, and skateboarding all maintain a serious risk of head injury. Head injury is a leading cause of accidental death and disability among children in the United States, resulting in over 100,000 hospitalizations every year. Studies have shown that children under the age of 14 are more likely to sustain head injuries than adults, and that children's head injuries are often more severe than those sustained by adults. In general, head injuries fall into two main categories—focal and diffuse. Focal injuries are limited to the area of impact, and include contusions, hematomas, lacerations and fractures. Diffuse brain injuries involve trauma to the neural and vascular elements of the brain at the microscopic level. The effect of such diffuse damage may vary from a completely reversible injury, such as a mild concussion, to prolonged coma and death.
Other activities, such as roller skating, in-line skating and skate boarding are typically conducted on the same types of surfaces as bicycling and can generate speeds similar to bicycling. Therefore, similar patterns of injury and benefits of helmet usage can be expected. Similar design considerations would apply for protective helmets for skating activities, in terms of impact attenuation. One difference between bicycling injuries and skating injuries is that, while 90 percent of bicycle-related head injuries occur on the front of the head, 80 percent of skating-related head injuries occur on the back of the head. Consequently, protective helmets for skating activities may have somewhat different design considerations in terms of coverage and location of protective padding. Protective helmets for aquatic activities, such as windsurfing, kayaking or water skiing, have similar design considerations in terms of impact attenuation, with the additional requirement for moisture resistance during long term immersion. Protective helmets for some activities, such as skiing or mountaineering, in addition to impact attenuation, have a need for a broad range of service temperatures.